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Author: O M
Motor Rebuild Shops
GM Castech Cylinder Heads
Motor Rebuild Shops Tech Solutions: I’m sure most of you know by now about GM’s 4.8L and 5.3L Vortec Gen III and Gen IV V8 engines with Castech cylinder head castings. GM has sent shops Technical Service Bulletin (TSB) for Castech specific cylinder heads that are prone to cracking. GM’s TSB #06-06-01-019B covers 4.8L and 5.3L engines with VINs V, T, M, B, Z from 2001-2006. Motor rebuild shops be sure to check for signs of cracking if you encounter these engines/vehicles. And when pricing these jobs be sure to allow for additional costs. The conditions may result in a slow loss of coolant with no sign of leakage, or continued coolant loss after overheating the engine from a cooling system failure. Castech heads are identified by a symbol that looks like a battery on the casting.
Adjusting Hydraulic Lifters for Proper PRE-Reload on your next engine rebuilding project more Tips for your Engine.
Since hydraulic lifters can compensate for thermal expansion of the engine, the adjustments can be made with the engine cold; hot adjustment is not necessary.
In order to adjust the reload the lifter must be properly located on the base circle or “Heel” of the lobe. At this position the valve is closed and there is no lift taking place.You will need to watch the movement of the valves to determine which lifter is properly positioned for adjusting.
The three most common factors that should be considered are installed height, camshaft type, and cylinder head valve spring pocket dimensions. Each consideration is equally critical to choosing the correct valve spring for your application.
To begin, your installed height should always be measured. This is important because the height at which a valve spring is installed can dramatically increase or decrease its rated coil bind clearance and opened/closed pressures. As this can lead to valve spring or camshaft failure, it is vital that you choose the correct spring for the installed height that your cylinder heads can accommodate.
The next consideration is camshaft type. In short, your valve spring pressure rating must be appropriate to the type of camshaft that you are using. Failure to run the correct pressure for the cam type will almost certainly result in engine damage. See the table below for general spring pressure guidelines based on cam type.
Finally note the physical diameter of the spring. Cylinder heads have pockets that can only accept certain diameter valve springs without machine work. To help circumvent the need for machine work, some manufacturers offer a wide selection of valve springs, as well as valve spring locators and shim kits to simplify the installation process.
The engine only responds to the actual movement of the valves. Since the valve cannot move until all the running clearance (valve lash) has been taken up, the amount of valve lash you use affects the engine’s performance.
If you decrease the amount of (hot) valve lash, for example, the valve will open slightly sooner, lift higher and close later. This makes the camshaft look bigger to the engine, because of a slight increase of actual running duration and lift. If you increase the amount of (hot) lash the opposite occurs. The valve will open later, lift less, and close sooner.
This shows the engine a smaller cam with slightly less actual running duration and lift. You can use this method on a trial basis to see what the engine responds to and keep the setting that works the best. Just remember, the more lash you run, the noisier the valve train will be. If the clearance is excessive it can be harsh on the other valve train components.
Therefore, for prolonged running of the engine Mayor`s does not recommend increasing the amount of hot lash by more than +.004″ from the recommended setting. And they do not recommend decreasing the hot lash by more than -.008″.
When you see a W on a viscosity rating it means that this oil viscosity has been tested at a Colder temperature. The numbers without the W are all tested at 210° F or 100° C which is considered an approximation of engine operating temperature. In other words, a SAE 30 motor oil is the same viscosity as a 10w-30 or 5W-30 at 210° (100° C). The difference is when the viscosity is tested at a much colder temperature. For example, a 5W-30 motor oil performs like a SAE 5 motor oil would perform at the cold temperature specified, but still has the SAE 30 viscosity at 210° F (100° C) which is engine operating temperature. This allows the engine to get quick oil flow when it is started cold verses dry running until lubricant either warms up sufficiently or is finally forced through the engine oil system. The advantages of a low W viscosity number is obvious. The quicker the oil flows cold, the less dry running. Less dry running means much less engine wear.
PROBABLE CAUSES
This damage is attributed to the thermal overload of the piston. There are two causes for this.
Abnormal combustion can be diagnosed via the following features:
• The bowl edge has been “gnawed off.”
• The injection nozzles display a poor spray pattern.
• The injection pressure and the delivery rate of the injection nozzles are set incorrectly.
• The top land shows seizure marks in the piston pin axis.
An abnormal combustion can be caused by a number of factors such as if the air-fuel mixture in the combustion chamber is too rich. This can be the result of the following:
• The air supply is reduced, e.g. the air filter is clogged.
• The fuel delivery is set incorrectly.
• The start of fuel delivery is set incorrectly.
• The nozzle needle is either wedged or stiff.
• The exhaust gas system is clogged.
There is ignition delay and misfiring, which may be caused by:
• The incorrect fuel or fuel with an insufficient cetane rating is being used, or there is gasoline in the diesel.
• The valves are leaky, resulting in compression loss.
• The protrusion is too small (i.e., there is insufficient compression).
• The air pre-warming is defective (especially for very low ambient temperatures).
Overheating of the piston crown can be identified via the following features:
• The combustion bowl is not damaged.
• An excellent spray pattern can be observed at the top of the piston.
The excessive temperature level of the piston crown can be caused by:
• The cooling oil nozzle is either bent, has become detached or has not been assembled (assembly error).
• The time between oil changes is too long. In this case, there is a risk of polymerization of the engine oil, especially when using biofuels, such as rapeseed and soybean oil, which can result in the cooling oil nozzles being clogged.
• Contamination, such as gasket residue, etc., prevents the required circulation in the oil circuit.
SOLUTION
• Set the injection amount and timing according to the manufacturer’s specifications.
• Check the injection nozzles for any leaks, the injection pressure and the spray pattern.
• Pay attention to correct alignment when assembling the cooling oil nozzles.
• Thoroughly clean the oil channels in the engine block, the crankshaft and the cylinder head.
• Make sure the pressure-regulating valve is functioning correctly.
• Ensure that the time between oil changes is much shorter when running the engine on biofuels.
If you are installing a new flat tappet camshaft in your engine, you must install new lifters. The lifter/lobe contact area is under a tremendous amount of pressure, and the lifter and lobe must wear in together.
The following reasons why you must install new lifters:
• A new lifter has a slight “crown.” A new cam has a slightly tapered face that causes the lifter to rotate.
• Installing a new cam with used lifters creates a concentrated contact pattern on the edge of the cam lobe
• Eventually, the contact wears out the edge of the lobe and lifter. Soon, the cam lobe wears down and the lifter stops rotating .
Piston Ring Installation Tips
File fit rings sets require filing of the top and 2nd rings to achieve the correct end gap. To properly measure the ring gap, the ring should be square in the bore one inch down from the deck.
Measure the ring end gap with a feeler gauge or equivalent device. Calculate the recommended ring end gap from the chart (Figure 1).
A proper ring gap filing tool must be used. Ring filing should be done in an inward direction and square to the sides of the ring. Be sure to de-burr all edges after filing.
Correct ring installation is critical. Only Manley rings, top ring has a shiny gray edge. When the top and 2nd ring has a dot, install dot side up. Unmarked top rings with an inner bevel install with bevel up. Unmarked 2nd rings with inner bevel install with bevel down.
Narrow rings (1.0/1.2mm) that aren’t marked or beveled can be installed with either side up. Do not overlap the ends of the oil ring expander. See orientation diagram (Figure 2).
Ring to piston groove back clearance should be a minimum of .005˝ deeper than the radial wall dimension of the piston ring. The piston ring should not stick out of the groove by any amount. Ring groove side clearance should be a minimum of .0015˝ to a maximum of .0030˝.
When included, the oil rail supports are installed on the bottom of the oil ring groove underneath the oil rail on Manley rings. The oil rail supports feature a special protruding dimple to prevent rotation of the oil rail support and the protruding dimple should be installed facing the bottom of the piston.
This dimple should be positioned directly in line with the piston pin. Keep the oil rail support gap 90° from the piston pin bore opening.
If any doubt exists, a solution of copper sulfate (CuSO4), which can be purchased at any drugstore or chemical supply house, should be applied with a cotton swab to an area of the liner. If the liner is not plated, a copper color will appear. If it is chrome plated no change will take place. Never use chrome in chrome.